The term "thermistor" is the generic name for devices made from materials the electrical conductivity of which is highly sensitive to variations in temperature. While thermistors are widely used as temperature sensors in a wide variety of industrial and consumer applications, they are particularly useful as elements of electric and electronic circuits. Thermistors having positive temperature coefficients (PTC thermistors) as well as thermistors having negative temperature coefficients (NTC thermistors) are used. Previously, thermistors having a high positive temperature coefficient of resistance (TCR) have been available, but the resistance range of those materials has been limited. Thus, the design flexibility of highly positive thermistors has been limited also. For example, doped BaTiO.sub.3 has a high positive TCR, but the useful range of temperatures is only between room temperature and 100.degree. C. Metals have a highly positive TCR but are limited in their usefulness by their low resistivity. On the other hand, silicon crystals, which do have both a highly positive TCR and a wide temperature range, can't be screen printed and therefore are limited in their usefulness also. In addition, RuO.sub.2 and RuO.sub.2 derivatives are known to have a good temperature range, but heretofore have had only small positive TCR values.